24 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



Copulation involves the same basic movements for all species 

 observed ; however, the temporal patterning is variable when unrelated 

 species are compared but uniform for a given species and frequently- 

 uniform for a genus. Figures 4, 5, and 6 summarize the copulatory 

 patterns for species of Meriones, Gerhillus, Perognathus, and Dipodo- 

 mys. Dipodomys is characterized by a long mount, whereas the other 



Figure 4. — Mount durations and temporal patterning of mounts for two species of 

 Dipodomys (vertical bars= mount and its duration; note the protracted mount with 

 terminal ejaculation in this species; A and B=Z). panamintinus; C=D. nitratoides). 



A I I lllliUllHIIH III 



liai I Ml II I II IIIIIHIHIII 



JILIL 



III! 



- ONE MINUTE 



Figure 5. — Mount durations and temporal patterning of mounts for two species of Perog- 

 nathus (A and B=P. calif amicus; C and D=P. parvus), 



A J-J HI I < »l— u U_l l—d 11 llllllll t I II , II ,11.1 nil I III I mil ml II II II nil II II M ill Ml I II 111 I Ml mini , 



6 III il iiiMnuniii II nil II iiii II III II mil LJ 1U_ 



H lllllllll l' lll"lll llll"lll 



Figure 6. — Mount durations and temporal patterning of mounts for Gerbillus and 

 Meriones (A and B=il/. unguiculaius; C=G. nanus). 



genera exhibit extremely short mounts. The Perognathus species and 

 Gerhillus nanus generally have one bout of mounting with ejaculation 

 on the terminal mount, whereas the more social Aleriones exhibits a 

 prolonged mount series with several apparent ejaculations. In this 

 patterning, Meriones resembles the golden hamster, Mesocricetus 

 auratus (Beach and Rabedaeu, 1959), and the Norway rat, Pattus 

 norvegicus (Beach and Jordan, 1956). 



